MyBatis 教程 - MyBatis插件（Plugins）开发

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MyBatis 允许你在已映射语句执行过程中的某一点进行拦截调用。默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：

• Executor (update, query, flushStatements, commit, rollback,
  getTransaction, close, isClosed)
• ParameterHandler (getParameterObject, setParameters)
• ResultSetHandler (handleResultSets, handleOutputParameters)
• StatementHandler (prepare, parameterize, batch, update, query)

这些类中方法的细节可以通过查看每个方法的签名来发现，或者直接查看 MyBatis 的发行包中的源代码。 假设你想做的不仅仅是监控方法的调用，那么你应该很好的了解正在重写的方法的行为。 因为如果在试图修改或重写已有方法的行为的时候，你很可能在破坏 MyBatis 的核心模块。 这些都是更低层的类和方法，所以使用插件的时候要特别当心。

通过 MyBatis 提供的强大机制，使用插件是非常简单的，只需实现 Interceptor 接口，并指定了想要拦截的方法签名即可。

自定义插件

需求：

把Mybatis所有执行的sql都记录下来。

代码实现

通过对 MyBatis org.apache.ibatis.executor.statement.StatementHandler 中的prepare 方法进行拦截即可。

prepare 方法签名如下：

Statement prepare(Connection connection, Integer transactionTimeout)
      throws SQLException;

自定义一个类，实现 org.apache.ibatis.pluginInterceptor 接口，代码如下：

package com.bytebeats.mybatis3.interceptor;

import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.plugin.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.util.Properties;

/**
 * ${DESCRIPTION}
 *
 * @author Ricky Fung
 * @date 2017-02-17 11:52
 */
@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class, Integer.class}) })
public class SQLStatsInterceptor implements Interceptor {
    private final Logger logger = LoggerFactory.getLogger(this.getClass());

    @Override
    public Object intercept(Invocation invocation) throws Throwable {

        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        BoundSql boundSql = statementHandler.getBoundSql();
        String sql = boundSql.getSql();
        logger.info("mybatis intercept sql:{}", sql);
        return invocation.proceed();
    }

    @Override
    public Object plugin(Object target) {
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
        String dialect = properties.getProperty("dialect");
        logger.info("mybatis intercept dialect:{}", dialect);
    }
}

这样一个插件就开发完成了，接下来需要在 mybatis-config.xml 文件中增加 plugins节点，完整配置如下：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

    <plugins>
        <plugin interceptor="com.bytebeats.mybatis3.interceptor.SQLStatsInterceptor">
            <property name="dialect" value="mysql" />
        </plugin>
    </plugins>
</configuration>

spring-mybatis.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:util="http://www.springframework.org/schema/util"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd
       http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
       http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <util:properties id="db" location="classpath:db.properties"/>

    <!-- 配置数据源 -->
    <bean name="parentDatasource" abstract="true" class="com.alibaba.druid.pool.DruidDataSource">
        <!-- 初始化连接大小 -->
        <property name="initialSize" value="1" />
        <!-- 连接池最大使用连接数量 -->
        <property name="maxActive" value="100" />
        <!-- 连接池最小空闲 -->
        <property name="minIdle" value="20" />
        <!-- 获取连接最大等待时间 -->
        <property name="maxWait" value="30000" />
        <property name="validationQuery" value="SELECT 1" />
        <property name="testOnBorrow" value="true" />
        <property name="testOnReturn" value="true" />
        <property name="testWhileIdle" value="true" />
        <!-- 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000" />
        <!-- 配置一个连接在池中最小生存的时间，单位是毫秒 -->
        <property name="minEvictableIdleTimeMillis" value="25200000" />
        <!-- 打开removeAbandoned功能 -->
        <property name="removeAbandoned" value="true" />
        <!-- 1800秒，也就是30分钟 -->
        <property name="removeAbandonedTimeout" value="1800" />
        <!-- 关闭abanded连接时输出错误日志 -->
        <property name="logAbandoned" value="true" />
        <!-- 监控数据库 -->
        <property name="filters" value="mergeStat" />
    </bean>

    <!-- trade数据源 -->
    <bean name="trade" init-method="init" destroy-method="close" parent="parentDatasource">
        <property name="driverClassName" value="#{db['trade.jdbc.driverClassName']}" />
        <property name="url" value="#{db['trade.jdbc.url']}" />
        <property name="username" value="#{db['trade.jdbc.username']}" />
        <property name="password" value="#{db['trade.jdbc.password']}" />
    </bean>

    <!-- admin数据源 -->
    <bean name="admin" init-method="init" destroy-method="close" parent="parentDatasource">
        <property name="driverClassName" value="#{db['admin.jdbc.driverClassName']}" />
        <property name="url" value="#{db['admin.jdbc.url']}" />
        <property name="username" value="#{db['admin.jdbc.username']}" />
        <property name="password" value="#{db['admin.jdbc.password']}" />
    </bean>

    <!--trade mybatis config-->
    <bean id="tradeSqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="trade" />
        <property name="mapperLocations" value="classpath*:mapper/trade/*Mapper.xml" />
        <property name="configLocation" value="classpath:mybatis-config.xml" />
        <property name="typeAliasesPackage" value="com.bytebeats.mybatis3.domain.trade" />
    </bean>

    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.bytebeats.mybatis3.mapper.trade" />
        <property name="sqlSessionFactoryBeanName" value="tradeSqlSessionFactory" />
    </bean>

    <!--admin mybatis config-->
    <bean id="adminSqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="admin" />
        <property name="mapperLocations" value="classpath*:mapper/admin/*Mapper.xml" />
        <property name="typeAliasesPackage" value="com.bytebeats.mybatis3.domain.admin" />
    </bean>
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.bytebeats.mybatis3.mapper.admin" />
        <property name="sqlSessionFactoryBeanName" value="adminSqlSessionFactory" />
    </bean>

    <!-- 配置事务 -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="trade" />
    </bean>

    <tx:annotation-driven transaction-manager="transactionManager" />

</beans>

maven依赖

    <properties>
        <java.version>1.7</java.version>
        <spring.version>4.2.7.RELEASE</spring.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!-- spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
            <exclusions>
                <exclusion>
                    <artifactId>commons-logging</artifactId>
                    <groupId>commons-logging</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.1.0</version>
        </dependency>

        <!-- db-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.26</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.25</version>
        </dependency>

        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.1</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.3.0</version>
        </dependency>

        <!--log-->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.21</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>log4j-over-slf4j</artifactId>
            <version>1.7.21</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <version>1.7.21</version>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.1.7</version>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.1.7</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

参考资料

MyBatis 插件（plugins）教程：http://www.mybatis.org/mybatis-3/zh/configuration.html#plugins

源代码下载

mybatis3-best-practice